90 J. D. Dana — Geological History of Oahu. 



II. Island of Oahu. 



From the map of Oahu, Plate 4, it is apparent that the island 

 (a) consists of two eroded mountain regions, an eastern and a 

 western, separated by a plain sloping gently downward to the 

 opposite coasts and upward toward the eastern mountains. A 

 more remarkable feature (b) is the long and high precipice 

 fronting northeastward, and thus facing the trade winds. Be- 

 sides these characteristics (c), there are lateral or subordinate 

 volcanic cones on the sea-border, of which Diamond Head and 

 its companions, Punchbowl, and the Koko Head craters on the 

 eastern cape (Plate 4, figs. 1, 2, 3), are examples. The island 

 is the only one of the group that has (d) a nearly continuous 

 coral reef fringing the shores. It owes to this reef the harbor 

 of Honolulu, the one good harbor of the group, and also the 

 possibility of a much larger and better one at Pearl River, 

 seven miles west of Honolulu ; the cutting of a channel 

 through the reef is all that is needed, as has long been recog- 

 nized, to make these capacious inner waters available for ship- 

 ping* Another interesting feature (e) is the existence of an 

 elevated coral reef on the borders of the island, having its in- 

 ner limits approximately indicated on the map by a dotted line. 



The facts on which the following account of the island is 

 based and the views deduced from them are for the most part 

 contained in my Expedition Geological Report. The visit in 

 1840 gave me nearly a month for study, which was indus- 

 triously employed in excursions over and around the island. 

 The accompanying map, on Plate 4, differs little, excepting in 

 improvement in outline and topography, from the colored geo- 

 logical map of my Report, and the outline of the elevated 

 coral reef and its coral rock and sand bluffs are copied from it. 

 The view of the tufa cones on the same plate are simply new 

 drawings from some of my old sketches. For fuller particu- 

 lars and some views not reproduced — as those of Kaneohe Point 

 and Aliapaakai, I refer to the Report. My recent visit (in 

 1887) gave me an opportunity for another excursion around a 

 large part of the island (taken with President Merritt), and 



* Honolulu, the capital of the Hawaiian Kingdom, was a collection of thatched 

 huts in 1840, with exceptions only in a Custom House, an unfinished coral-rock 

 church, and a few dwellings of civilized aspect. To-day it is city-like in its 

 houses, its streets electrically lighted, its public squares, large Hospital grounds, 

 spacious Government buildings — among them a palace good enough for any po- 

 tentate — and its exceUent hotel ; and, through the addition of groves and avenues 

 of introduced palms and tropical trees (some of which are always in flower or 

 fruit) it is fast becoming a place of ideal beauty. Honolulu is the center of all 

 the island activities, including inter-island navigation. It is not out of place to 

 repeat here that steamers start every week or two for Hawaii and Kilauea — one 

 route by Hilo to Keauhou, and thence up by horseback and wheels, the other by 

 Punaluu on the south coast, where there is a good hotel and a carriage road all 

 the way to the volcano. A carriage road from Hilo to Kilauea is in prospect. 



